Free piston pumping engine



July 15, 1969 A. URBEN FREE PISTON PUMPING ENGINE 2 Sheets-Sheet 1 FiledMay 24, 19,67

Inventor: Adcluro Urben BY fa ATTORNEYS July 15, 1969 A. URBEN FREEPISTON PUMPING ENGINE 2 Sheets-Sheet 2 Filed May 24, 1967 Inventor:

A d ouro U r be n United States Patent 3,455,501 FREE PISTON PUMPINGENGINE Adauto Urben, Winterthur, Switzerland, assignor to SulzerBrothers Limited, Winterthur, Switzerland, a Swiss company Filed May 24,1967, Ser. No. 640,884 Int. Cl. F02b 71/06; F04b 31/00; F02d 39/10 US.Cl. 230-56 1 Claim ABSTRACT OF THE DISCLOSURE There is disclosed a freepiston pumping engine including two pairs of pumping units eachincluding a pumping piston, two driving pistons and two synchronizingpistons with each piston working in a separate stationary cylinder.Junction conduits interconnect the synchronizing cylinders of thepumping units in pairs. A separate delivery conduit having across-section not greater than 10% of the crosssection of the junctionconduit unobstructedly connects a pressure source to each junctionconduit.

BACKGROUND OF THE INVENTION Field of the invention The invention relatesto free piston engines useful as pumps, compressors and the like.

The prior art Free piston pumping engines have been heretofore proposed,but difiiculty has been experienced in holding the piston units thereofin the proper relative phases. The mechanical synchronizing deviceshertofore proposed have been relatively complicated and have not in allinstances been readily applicable.

Summary of the invention It is an object of the invention to produce afree piston engine substantially simpler than those heretofore proposedin respect of the phasing or synchronizing devices employed, morecompact as regards the space required for these synchronizing means, andhaving greater flexibility in the disposition of the various parts ofthe engine.

Brief description of the drawing The invention will now be furtherdescribed in terms of a non-limitative exemplary embodiment and withregard to the accompanying drawings, wherein:

FIG. 1 is a diagrammatic perspective view of a free piston engineaccording to the invention; and

FIG. 2 is a diagram showing the synchronizing or phasing interconnectionof the piston units of the engine of FIG. 1, elements of FIG. 1appearing in a developed view in FIG. 2.

The free piston engine of FIG. 1 includes four piston units a, b, c anda, each of which includes a central pumping or compressor piston 1 withinternal combustion engine or driving pistons 2 and 2' on either side ofthat pumping piston, synchronizing pistons 10 and 10' likewise onopposite sides of the piston 1, and a piston rod to which the fivepistons are affixed. The pumping pistons 1 move in pumping cylinders 3,the engine pistons in engine cylinders 4 and 4', and the synchronizingpistons in synchronizing cylinders 11 and 11. These five cylinders arefixed with respect to each other and with their associated piston unitmake up one of the four pumping units of the engine of FIG. 1. Thecylinders have been shown only fragmentarily for purposes ofillustration.

The pumping cylinders are limited by partitions 21 and 22 which serve asheads for the synchronizing cylinders 11 and 11'. Inlet and outletvalves, together with pump intake and delivery conduits, not shown, areprovided in each of the pumping cylinders on each side of the pumpingpiston therein. These elements may be conventional in nature and havetherefore not been shown. The engine cylinders are closed by heads 23and 24 which with those cylinders may include fuel and combustion airinlet and exhaust valves and, optionally, ignition means. The enginepistons may operate on either two or four stroke cycles, and may employspark ignition or may be of the diesel type. All of these elements,which may likewise be conventional, have not been shown in the drawing.

As is shown in FIG. 1, the axes of the piston units a, b, c and a, andtherefore the piston rods 5, are parallel to each other and are disposedat the angles of a quadrilateral parallelogram, which may for example bea square. For balancing of the linear and moment inertia forces thephasing of the piston units is such that the pistons of two diagonallyopposite units are in the same phase while circumferentially adjacentunits are in opposite phase. Thus, in FIG. 1, when the pistons of theunits a and c are at the lower limit of their travel (as seen in thatfigure), the pistons of the units b and d are at the upper end of theirtravel. When the pistons of the units a and c are moving upwardly thoseof the units b and d are moving downwardly and vice versa.

For synchronization of the piston motions, i.e. for preservation thereofin the relative phase relation just described, the piston units areprovided each with two synchronizing pistons 10 and 10' which cooperatewith synchronizing cylinders 11 and 11'. In each piston unit the twosynchronizing pistons, like the two engine pistons, are in oppositephases of their cyclical motions with respect to their cylinder heads.Thus when an engine piston 2' is at the top of its stroke, adjacent itscylinder head 24, the engine piston 2 of that unit is at the bottom ofits stroke, at maximum distance from its cylinder head 23. Similarly,when a synchronizing piston 10 is at the top of its stroke, adjacent itscylinder head 22, the synchronizing piston 10' of that unit is at thebottom of its stroke, at maximum distance from its cylinder head 21. Thespace between each synchronizing piston and the head of the cylinder inwhich it moves may be referred to as a synchronizing space.

The synchronizing spaces of piston units which operate out of phase arecoupled together by junction conduits 12. More particularly, theconduits 12 interconnect, as between out-of-phase pumping units,synchronizing spaces thereof which are similarly positioned on theirrespective pumping units so as to be themselves out of phase when theirpumping units are out of phase, in accordance with the intendedoperation of the engine. Thus the synchronizing space of cylinder 11 onunit d is connected via a junction conduit 12 with the synchronizingspace of cylinder 11 on unit a, while the synchronizing space ofcylinder 11 on unit a is connected by another junction conduit 12 to thesynchronizing space of cylinder 11' on unit b. Similarly thesynchronizing spaces of cylinders 11 of units b and c are interconnectedand, lastly, the synchronizing spaces of cylinders 11 on units 0 and dare interconnected. The cylinders 11 and 11' and the conduits 12 arefilled with a hydraulic fluid such as oil and constitute as to each suchpair of coupled piston units a set of communicating vessels.

FIG. 2 shows a diagram of the synchronizing pistons and cylinders in theengine of FIG. 1, and of their interconnecting conduits 12, as if theengine of FIG. 1 had been developed on a plane. For simplicity andclarity the pumping and engine pistons have been omitted from FIG. 2.Thus, the axes of the four piston units which in the structure of FIG. 1are disposed at the corners of a parallelogram, lie in FIG. 2 in acommon plane. The conduit 12 leading to the right from the uppersynchronizing cylinder 11 of the piston unit d is coupled with theconduit 12 extending to the left from piston unit a as indicated by thedash line in FIG. 2..

FIG. 2 also shows apparatus for supplying of hydraulic fluid to thesynchronizing cylinders. Since a certain amount of leakage isunavoidable, as indicated by the arrows V in FIG. 2, the individualjunction lines 12 are connected through delivery lines 13 to a commonsupply line 14 fed from a pump 15. This pump maintains the hydraulicfluid in the cylinders 11, 11' and conduits 12 under a pressure aboveatmospheric and thereby insures replacement of hydraulic fluid lostthrough leakage.

The supply line 14 can be provided with a check valve 16, if necessaryin view of the nature of the feed pump 15.

As is evident from FIG. 2, the delivery lines 13 of the synchronizingsystem are connected together by means of a supply line 14. This has theresult that small irregularities in the synchronous motions of thepiston units can be tolerated, the resultant motions of hydraulic fluidin the delivery lines 13 exerting a substantial damping efiFect so thatcritical oscillations of the system are avoided and so that oscillationsin general are rapidly damped out. To this end the delivery lines 13 areso dimensioned that they exert a strong throttling effect on thehydraulic medium by comparison to the effect thereon of the junc tionlines 12. Thus with normal length ratios the crosssection of thedelivery lines should amount at most to 10% of the cross-section of thejunction lines 12. The term normal length ratios may be understood asthe length ratios of delivery lines 13 to junction lines 12 each of thembeing made no longer than absolutely necessary. In a particular casewith a diameter of 40 cm. for the synchronizing pistons 10 and 10' andwith a motion frequency for the pistons of 350 cycles (i.e. 700 strokes)per minute, a cross-section of 200 square centimeters for the junctionlines 12 and of one square centimeter for the delivery lines 13 wasfound suitable.

As a result of the fact that all of the junction lines 12 are connectedto each other via the delivery lines 13 and supply line 14, it ispossible to effect or to tolerate an axial shift of all of the pistonunits, for example, in the event of too heavy a supply of fuel to thedriving pistons on one side of the pumping pistons. This requires thatthe pistons be subjected to a centering action independently of theoperation of the synchronizing pistons. In the embodiment illustrated,this centering action is provided by the buffering compression action inthe engine and pumping cylinders. Advantageously, supplementary butterspaces and synchronizing means may be employed in accordance with thedisclosure of the copending application of Anton Steiger entitled FreePiston-Type Internal Combustion Engine which is assigned to the assigneehereof and which has been filed concurrently with the presentapplication. Buffers employing mechanical springs may also be used assupplementary synchronizing means.

While the invention has been described herein in terms of a presentlypreferred embodiment, the invention itself is not limited thereto butrather comprehends all modifications on and departuresfrom thatembodiment properly falling within the spirit and scope of the appendedclaim.

I claim:

1. A free piston internal combustion pumping engine comprising aplurality of pumping units, said plurality being an even multiple oftwo, each of said units including a pumping piston, a driving piston, asynchronizing piston, means coupling said pistons together, and apumping cylinder, an engine cylinder and a synchronizing cylindersurrounding said pumping, driving and synchronizing pistonsrespectively, said engine further comprising junction conduitsinterconnecting the synchronizing cylinders of said pumping units inpairs, a source of hydraulic fiuid under pressure, and a separatedelivery conduit unobstructedly connecting said source to each of saidjunction conduits, said delivery conduits having each a cross-sectionnot greater than 10% of the cross-section of the junction conduits towhich they respectively connect.

References Cited UNITED STATES PATENTS 2,139,425 12/1938 Steiner 230-56XR 3,106,896 10/1963 Van Der Lely et al. 10354 3,182,895 5/1965 Panhard230-56 ROBERT M. WALKER, Primary Examiner US. Cl. X.R. l23-46

